1. Field of the Invention
This application relates to orthoses, and more particularly to ankle-foot orthotic braces which have a joint for allowing movement along a rotational axis.
2. Detailed Description of Related Art
Ankle foot orthoses are commonly used as foot, ankle, and leg braces for improving movement. Years ago a leg brace would consist of two metal bars and a stirrup attached to the sole of the shoe. A horizontally positioned padded, metal band, contoured to the back of the leg calf, would connect the two metal bars. A broad strap across the anterior section of the calf would hold the brace in place. This type of brace has limited use today, but is not considered to be state of the art orthotic management. This type of device lacks biomechanical control of the foot and ankle and is cumbersome and heavy. It would be very difficult to adapt this brace to athletic applications since the metal bars would pose a hazard for the user, and possibly to other participants in the sport.
A modern ankle foot orthosis, being a device that applies biomechanical forces to a body segment, is usually fabricated from thermoplastics. The thermoplastic is heat molded over a positive mold similar in shape to the patient's limb, then cooled, and trimmed. Often the thermoplastic is formed into rigid laminates of non-resilient material. Ankle joint motion in the orthotic device is often provided by a mechanical hinge type joint at the ankle joint. Once again, these devices may pose a hazard to the user and others, especially when used in contact sports.
An existing fundamental problem of orthotic management is that a rigid orthosis, which does not allow plantar flexion of the ankle, will also prevent extension of the hip and knee and causes instability in the hip and knee. Balance at the foot-ankle complex cannot properly develop because activity and sensation of movement is limited, with resultant muscle wasting. These rigid orthosis are sometimes utilized for rehabilitating athletes, but provide a potential for possibly injuring the user or other participants in a sport.
Current orthotic technology does not allow triplanar activity of the foot and ankle in stance phase found in normal gait. The use of very thin or more flexible plastics has been attempted to allow more motion in the foot and ankle. Much of the benefit of wearing an orthosis is lost when using very flexible, but still non-deformable and non-resilient, plastics, however, in cases where significant control is needed for spastic muscle activity, pathomechanical deformities, or athletic activities following an injury or other problem. The very flexible plastics reduce stability to allow mobility. Allowing motion is not the same as promoting and controlling more normal motion. The disclosure of the present invention promotes and controls more normal motion.
For many patients who require the use of an ankle-foot orthosis, current orthotic technology does not adequately address the dynamic changes that occur in the foot and ankle complex during the gait cycle. Triplanar motion of the foot and ankle requires a dynamic response. Current technology either positions the segments of the foot in a static position or allows motions to occur by reducing the corrective forces. The use of a mechanical ankle joint with a rigid frame may provide motion of the talocrural joint in the sagittal plane, however complex motions required within the foot, are restricted from a normal biomechanical response because of the static forces applied by the brace. Optimal orthotic management should control abnormal motion by restricting specific motion during specific events of the gait cycle. This cannot be achieved by holding the segments of the foot in an uniform position throughout the gait cycle. The foot must remain a mobile entity that engages in the normal activity of gait, but is prevented from abnormal motion. Because the needs of the corrective forces of the foot and ankle complex differ within different events of the gait cycle, a need exists for an orthosis which is dynamic in its application of corrective forces.